View source for XO1.75 A2 A3 Changes

These are the changes planned for the [[XO_1.75_B1|XO-1.75 B1 prototype]], from the [[XO_1.75_A2|A2 prototypes]].

=A2 Electrical Fixes=
These changes fix problems in the A2 prototypes:

==SD power==
These correct a mistake in Embedded Controller pin assignments for the SD power control signals.

* Depopulate R335 and R345.
* Remove Q16, and short pins 2 and 3 (marked I and O).
* Remove Q16, and short pins 2 and 3 (marked I and O).

==VMEM stability==
This corrects an undercompensation of the +1.5V memory power supply, and also delays the turn-on of the memory termination power supply.

* Change PR49 to 22K.
* Change PR52 to 47K.
* Populate PC37 with 0.1 uF.

==eMMC==

* Populate R95 with 10K.
* Connect BOOT_DEV_SEL to CN21.10
* Use +3.3V_SD1 to power the eMMC instead of +3.3V_NAND

==J2==

The MISO and MOSI pins on J2 are swapped (the SOC GPIO map was wrong).

SPI_MISO should be connected to U10.2, J2.1, and U11.AD15 (GPIO43)

SPI_MOSI should be connected to U10.5 , J2.4, and U11.AE15 (GPIO44)

=A2 Layout Fixes=

- Bring GPIO04 (pin 5) to a user-probeable pad, for brick recovery purposes.  (It may need to be grounded during EC flash reprogram.)

=Planned Feature Changes=


[[Category:Hardware]]
[[Category:XO-1.75]]